Accession ARO:3002857
CARD Short NamedfrA26
DefinitiondfrA26 is an integron-encoded dihydrofolate reductase found in Escherichia coli.
AMR Gene Familytrimethoprim resistant dihydrofolate reductase dfr
Drug Classdiaminopyrimidine antibiotic
Resistance Mechanismantibiotic target replacement
Resistomes with Perfect MatchesCitrobacter freundiiwgs, Enterobacter cloacaewgs, Enterobacter hormaecheiwgs, Klebsiella pneumoniaewgs, Klebsiella quasipneumoniaep+wgs
Resistomes with Sequence VariantsCitrobacter freundiiwgs, Enterobacter cloacaewgs, Enterobacter hormaecheiwgs, Klebsiella pneumoniaewgs, Klebsiella quasipneumoniaep+wgs
Classification9 ontology terms | Show
Parent Term(s)3 ontology terms | Show
+ trimethoprim resistant dihydrofolate reductase dfr [AMR Gene Family]
+ derives_from antibiotic sensitive dihydrofolate reductase
+ confers_resistance_to_antibiotic trimethoprim [Antibiotic]

Grape M, et al. 2007. Antimicrob Agents Chemother 51(5): 1863-1864. Two new dfr genes in trimethoprim-resistant integron-negative Escherichia coli isolates. (PMID 17307981)


Prevalence of dfrA26 among the sequenced genomes, plasmids, and whole-genome shotgun assemblies available at NCBI or IslandViewer for 413 important pathogens (see methodological details and complete list of analyzed pathogens). Values reflect percentage of genomes, plasmids, genome islands, or whole-genome shotgun assemblies that have at least one hit to the AMR detection model. Default view includes percentages calculated based on Perfect plus Strict RGI hits. Select the checkbox to view percentages based on only Perfect matches to AMR reference sequences curated in CARD (note: this excludes resistance via mutation as references in protein variant models are often wild-type, sensitive sequences).

Prevalence: protein homolog model (view sequences)

SpeciesNCBI ChromosomeNCBI PlasmidNCBI WGSNCBI GI
Citrobacter freundii0%0%0.19%0%
Enterobacter cloacae0%0%0.32%0%
Enterobacter hormaechei0%0%0.04%0%
Klebsiella pneumoniae0%0%0.08%0%
Klebsiella quasipneumoniae0%0.21%0.39%0%
Show Perfect Only

Detection Models

Model Type: protein homolog model

Model Definition: Protein Homolog Models (PHM) detect protein sequences based on their similarity to a curated reference sequence, using curated BLASTP bitscore cut-offs. Protein Homolog Models apply to all genes that confer resistance through their presence in an organism, such as the presence of a beta-lactamase gene on a plasmid. PHMs include a reference sequence and a bitscore cut-off for detection using BLASTP. A Perfect RGI match is 100% identical to the reference protein sequence along its entire length, a Strict RGI match is not identical but the bit-score of the matched sequence is greater than the curated BLASTP bit-score cutoff, Loose RGI matches have a bit-score less than the curated BLASTP bit-score cut-off.

Bit-score Cut-off (blastP): 300

>gb|CAL48457.1|+|dfrA26 [Escherichia coli]

>gb|AM403715.1|+|303-854|dfrA26 [Escherichia coli]